Yes, Winchester did offer IMP-MOD choked and marked guns in 12, 16 and 20 Gauge, along with CYL, WS-1, IMP-CYL, WS-2, MOD and FULL.To give you heads up Winchester model 12 never produced a imp/mod barrel
I have a full 26 inch factory solid rib on gunbroker. Seller is Lion H E. It has freckling on receiver, non original wood. Also plain barrel 25.5 inch 20 ga marked imp. Cup. I bought it ,guy said it was 28" and was sold as is. This gun is original condition word be excellent for barrel change or conversion.